Wrapper script to make commands that look like linking run in serial

lock-linking

#!/bin/sh

# Run a command with a lock if it looks like it is a linker command: that is,
# if none of its arguments are -c.

# Then you can do a build where compilation is parallel but linking is serial
# by doing something like (for llvm/clang):
# make -j4 'CXX=lock-linking /tmp/llvm-build-lock clang++'

LOCKFILE="$1"
shift
for I in "$@"; do
	if [ $I = "-c" ]; then
		# Not a linker command, just run it
		exec "$@"
	fi
done

# Run the linker command under the lock
flock "$LOCKFILE" "$@"